Fig. 5

Engineering sulfur defects into MoS₂ QDs through stoichiometric reaction control. a Adjusting precursor ratios produces three kinds of MoS₂ suspension in pure water. TEM images show narrow size distribution. Scale bar: 50 nm. b Different stoichiometry does not affect overall size of QD MoS₂. (Distributions derived from at least n = 200). HRTEM images show dislocations and distortions of lattice planes in MoS₂ QDs due to intrinsic defects. Scale bar: 2 nm. c XRD show gradually enlarged lattice constants with decreasing stoichiometry in three MoS₂ QDs. d PL spectrum show different emission intensities of the three MoS₂ QDs at the same optical absorption. e XPS reveal the defect engineering was in the form of MoO_xS_2-x by the substitution of oxygen for sulfur. f Structural model of the reaction pathway of MoS₂ QDs and defect engineering in MoS₂ QDs as a function of precursor stoichiometry